| 摘要 |
PURPOSE:To enable the detection of the defect on a surface with high S/N ratio, by setting the angle between the normal on the surface of a specimen and the incident angle of irradiated light at 15-55 deg. and detecting the scattered light and specular reflected light of <20 deg. angle to the incident direction. CONSTITUTION:A laser light source 22 disposed in the diagonal direction intersecting orthogonally with the traveling direction of a continuous casting slab 20 on the lateral side of the traveling line of said slab irradiates external light in such a way that the angle theta1 between the normal on the surface of the slab 20 and the incident direction of the irradiated light attains 15-55 deg.. The laser light 22a is expanded to a belt shape up to the necessary visual field on the slab 20 by a cylindrical lens 24. On the other hand, a photodetection camera 26 disposed on the same lateral side as the light source 22 of the slab traveling line detects the scattered and reflected light of <20 deg. angle theta2 to the incident direction of the detected light. The outputs of the camera 26 and a camera 28 for detecting regular reflected light are compared in a comparator 34 via signal processing circuits 30, 32, and only the defect signal removed of the spurious defect signal by a scale, etc. is outputted. |
